[ARM] 3485/1: i.MX: MX1 SD/MMC fix of unintentional double start possibility

Patch from Pavel Pisa

The clock starting imxmci_start_clock() function contains hardware
issue workaround, which repeats start attempt, if SDHC does not react on
the first trial. But the second start attempt can be taken even, if the
first succeed and test code misses time limited clock running phase
due to delay caused by schedule to other task or some another device
interrupt. This change enables to detect such situation.
The performance is not issue, because usually at full clock rate
only about six loops in delay cycle are needed.

Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>